Files (addressing something the app stores)

Summary#

A stored file is addressed by URL, and which URL you ask for is an access decision.

using Osyrin.Storage;

[Principal] entity User { [MaxLength(200)] string Email; }

entity Item { [Required, MaxLength(200)] string ImagePath; }

// Anyone may fetch this — it is an asset, served to whoever asks.
string PublicImage(Item item) { return File.Url(item.ImagePath); }

// This one belongs to somebody, so the URL carries its own expiring grant.
string PrivateReport(User user) { return File.SignedUrl("reports/" + user.Id + "/q3.pdf"); }

Description#

File.Url is pure sugar over the serving route — an app-relative path becomes /_osy/files/…, which means it works directly inside a render argument. It grants nothing: what it addresses is served to whoever asks, so it is right for assets and wrong for anything a person owns.

File.SignedUrl is the other case, and it is the one to reach for by default when the file belongs to somebody: the URL carries its own time-limited grant, so sharing it is a decision with an expiry rather than a permanent one.

See also#

• File.Url — the public address, and where it is safe
• File.SignedUrl — a time-limited grant to one caller